Using horst I've discovered that the major reason our WiFi network sucks is because 90% of the packets are sent at the 6mbit rate. Most of the rest show up in the 12 and 24mbit zone with a tiny fraction of them using the higher MCS rates.
Trying to couple the radiotap info with the packet decryption to discover the sources of those low-bit rate packets is where I've been running into difficulty. I can see the what but I haven't had much luck on the why.
I totally agree with you that tools other than wireshark for analyzing this seem to be non-existent.